When fearful people speak of “aliens”, they don’t necessarily refer to extraterrestrial creatures from outer space. Birds can be alien species as well. 

When a species of animals native to one part of the world migrate to another region, either when getting there by themselves or by being smuggled or escaping from captivity, havoc can ensue. Invasive species of parrots/parakeets from South America and India that have reached Europe and Israel – located at the meeting point of three continents – are endangering agriculture. 

Ecologist Dr. Assaf Shwartz of the Technion-Israel Institute of Technology is leading leads a multi-national team investing the effect of such invasive species: “It is important to prevent the release of non-native species in nature,” he writes in the latest issue of the journal in Neobiota and in the umbrella of ParrotNet, a European network of scientists, practitioners, and policy-makers dedicated to research on invasive parrots, their impacts and the challenges they present. 

The European Cooperation in Science and Technology (COST Actions) is funding ParrotNet’s efforts to better understand why parakeets are highly successful invaders, how their agricultural, economic, societal and ecological impacts across Europe can be predicted, the means to fight the invasion and to help policymakers manage to cope with the challenges posed by invasive alien species. 

Non-native parrots can cause substantial agricultural damage and threaten native biodiversity, although impacts vary strongly depending on where these parrots have been introduced. Brought to Europe as pets, escaped or released parrots have established numerous wild populations across Europe. Tens of thousands of “alien” ring-necked and monk parakeets already make up the bulk of Europe’s parrot species, and several other species are also gaining a foothold. 

There are today more than 200 flocks of parakeets originating in South America and India. “These are parrot species that were brought to Israel as pets and some of them were released or escaped from their cages and created huge free populations,” said Shwartz of the Technion’s Faculty of Architecture and Town Planning. “These populations are growing every year, and today there are more than 10,000 ring-necked parakeets and monk parakeets in Israel.”

Introduced parrots can damage the environment, but severe impacts are rare and localized. Most reports of damage were linked to the widespread and locally abundant ring-necked and monk parakeets. Studies show that in their native ranges, both species can, and regularly do, inflict large crop losses, but in temperate Europe, expectations of comparable widespread and severe damage to agriculture have so far failed to materialize. Severe impacts on crops were recorded in Mediterranean Europe. 

Competition with native species presents a more serious problem, especially for ring-necked parakeets as they can compete with native species for food and breeding sites. In the Americas, monk parakeets are notorious for the damage their stick nests cause to power infrastructures by catching fire, yet very little evidence for such problems exist in Europe. Reported impacts for other parakeet species in Europe are virtually nonexistent, probably because these species have been introduced more recently and currently exist as relatively small and localized populations.

The study also highlights that differences in the type of damage, and the way they are reported and summarized influences the outcomes of invasive species impact assessments. The generalized threat level that invasive species pose is often based on their worst known impacts, whilst the capabilities of a species to do damage often requires specific circumstances. 

While this is relevant information for identifying those invaders that can potentially have major impacts, it is not necessarily representative of the impacts the species is likely to have when introduced to a new area, wrote Shwartz. Similarly, including damage reports from the native range or from other invaded ranges typically results in higher threat level estimates compared to what actually has been observed in Europe.

“The ring-neck parakeets and monk parakeets have already established large populations in Israel and in Europe,” he continued.  “Ultimately, the decision on ways to reduce the damage is in the hands of the decisionmakers, but as scientists, it is important to note that the best way to combat species invasions is to prevent the release of non-native species in nature. Studies have shown that in the islands it is possible to eradicate/mitigate populations of invaders (for example in Seychelles), but on large continents, in areas such as Israel and Europe, there is no ‘silver bullet’ solution to the problems, so it is important to conduct wide cost-benefit studies.“